Abstract
Moss-dominated biocrusts (moss crusts) are a feasible approach for the ecological restoration of drylands, but difficulty obtaining inoculum severely limits the progress of large-scale field applications. Exogenous microorganisms could improve moss growth and be conducive to moss inoculum propagation. In this study, we investigated the growth-promoting effects and potential mechanisms of exogenous microorganism additives on moss crusts. We used an incubator study to examine the effects of inoculation by heterotrophic microorganisms (Streptomyces pactum, Bacillus megaterium) and autotrophic microorganisms (Chlorella vulgaris, Microcoleus vaginatus) combined with Artemisia sphaerocephala gum on the growth of Bryum argenteum, the dominant moss crusts species in sandy deserts. Amplicon sequencing (16S and 18S rRNA) and PICRUSt2 were used to illustrate the microbial community structure and potential function in the optimal treatment at different developmental stages. Our results showed that exogenous microorganisms significantly promoted moss growth and increased aboveground biomass. After 30 days of cultivation, the Streptomyces pactum (1 g kg–1 substrate) + Chlorella vulgaris (3.33 L m–2) treatment presented optimal moss coverage, height, and density of 97.14%, 28.31 mm, and 2.28 g cm–2, respectively. The best-performing treatment had a higher relative abundance of Streptophyta—involved in moss growth—than the control. The control had significantly higher soil organic carbon than the best-performing treatment on day 30. Exogenous microorganisms improved eukaryotic community diversity and richness and may enhance soil microbial functional and metabolic diversity, such as growth and reproduction, carbon fixation, and cellulose and lignin decomposition, based on functional predictions. In summary, we identified the growth-promoting mechanisms of exogenous additives, providing a valuable reference for optimizing propagation technology for moss inoculum.
Highlights
Most dryland ecosystems are regulated and stressed by abiotic factors, especially water, so it is hard for drylands to support the growth of abundant and continuously distributed vascular plants (Li et al, 2009)
The moss crusts were crushed into stem and leaf fragments (1– 3 mm) using a plant sample pulverizer (IZARA-2500C, Jinhua, China) and mixed well for moss inoculum cultivation
Our results suggest that adding exogenous microbes enhances moss coverage and could be a useful technique for propagating moss inoculum
Summary
Most dryland ecosystems are regulated and stressed by abiotic factors, especially water, so it is hard for drylands to support the growth of abundant and continuously distributed vascular plants (Li et al, 2009). The patchy distribution of vascular plants provides a suitable ecological niche for biological soil crusts (biocrusts) colonization, covering 40% of the dryland surface area (Li et al, 2009; Lan et al, 2012). Biocrusts are a community of cyanobacteria, algae, lichens, bryophytes, and other microorganisms integrated with topsoil particles (Eldridge and Greene, 1994; Belnap et al, 2016) that provide several ecosystem services, including nitrogen and carbon fixation (Beymer and Klopatek, 1991; Billings et al, 2003), soil stability (Zhang et al, 2007), microhabitats for other organisms (Liu et al, 2013), and important interactions with vascular plants (Eldridge and Greene, 1994; Chaudhary et al, 2009; Li et al, 2009). If drylands rely on natural recovery only, there will be a lack of stable and fully functional biocrusts for many years after disturbance. Manual intervention, such as field inoculation, is vital for dryland restoration
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